The present invention relates to gas flow control valves and more particularly to demand valves for breathing apparatus.
In one aspect, the invention is concerned with a valve incorporating a so-called "balanced piston" valve member, which is characterised by low operating forces and an ability to operate consistently over a range of supply pressures. Such a valve for use in underwater diving equipment is described and illustrated schematically in U.S. Pat. No. 3,647,175. It is an aim of the present invention to adapt this principle to use in a positive pressure demand valve of compact construction and efficient operation.